This invention relates to catheters useful in cardiac angiography and more particularly to such catheters especially suited for the injection of a radiopaque dye into the right coronary artery.
Coronary angiography or arteriography involves the insertion of a hollow catheter into an artery at a remote point such as an arm or leg. The catheter is typically guided to the heart itself by a guide wire over which the catheter rides. The guide wire is removed before use of the catheter. Once the catheter is properly placed, a radiopaque dye is injected through the lumen of the catheter so that an x-ray machine or fluoroscope may be used to determine the physical condition of the particular part of the heart under study.
The exact placement of the tip of the catheter in the heart depends upon the type of coronary angiography to be performed. For example, in non-selective angiography the tip of the catheter is positioned in the aorta itself so that both the left and right coronary arteries can be simultaneously injected with radiopaque dye. In selective angiography, on the other hand, the tip of the catheter is actually placed in the ostium of the coronary artery which one wishes to study, in this case the right coronary artery, and the radiopaque dye is injected directly into that artery. Selective angiography produces pictures having sharp images which are extremely helpful in diagnosing and treating coronary diseases.
Heretofore, some catheters used for selective right coronary artery angiography have not always retained their positions in the ostium of the right coronary artery during the procedure. As a result the radiopaque dye was not wholly injected into the right coronary artery and the images obtained were not as satisfactory as could be desired. While some catheters fall or pop out of the ostium, others are difficult to insert properly into the ostium initially. In addition, some prior catheters have been known to dive too far into the right coronary artery itself, which can cause a spasm of the artery.
It is also important that the catheter be made of the proper materials. Although a certain hardness and rigidity is desired to allow maintain the catheter in position in the ostium once the tip is inserted therein, a catheter which is too rigid is difficult to position properly. Moreover, a relatively hard tip on the catheter can result in the dislodging of plaque from the vessel walls, which is not desirable.
Several catheters have been proposed or developed to solve some of the above difficulties. For example, U.S. Pat. No. 3,935,857 to Co discloses a cardiac catheter which is alleged to be useful in both right coronary and left coronary selective arteriography. On the other hand, Dr. Melvin P. Judkins in Chapter 7 of Coronary Arteriography and Angioplasty "1985" (McGraw-Hill) discloses differently shaped catheters for right coronary and left coronary selective arteriography.
The Judkins right coronary catheter has a preformed curvature which is designed to assist in the placement of the catheter tip in the ostium of the right coronary artery and to help hold the tip in place during the procedure. Because of the particular configuration chosen for the Judkins right coronary catheter, it is necessary for the catheter to be made in a number of different sizes to accommodate different patients. It is also necessary in using the Judkins right coronary catheter to physically rotate the catheter approximately 180 degrees once the catheter is in the heart to make it assume the proper position to enter the ostium of the right coronary artery. As Dr. Judkins points out in the aforementioned chapter, this rotation must be done very slowly and commonly gives rise to error in placement of the catheter.